there is trouble klinkenberg syntax function

can anyone help me, why my MatLab version can't run the klikenberg syntax function, should i install the tools, and what the tool box?

and here is the script,

function klinkenberg
Pm=3800;  % Initial Reservoir Pressure
% length of block 
dx = 22; 
dy = 12; 
dz = 2;
dt = 10;    % Time Interval
T = 1000;   % Total days
n = 5;      % no. of matrix
i=1; j=1; k=1;
Ax=dy*dz;
Ay=dx*dz; 
Az=dx*dy;
B(n,n,n) = 0;
S(n,n,n) = 0; 
W(n,n,n) = 0;
E(n,n,n) = 0;
N(n,n,n) = 0;
A(n,n,n) = 0;
X(n,n,n) = 0;
m=T/dt;
P(n,n,n,m) = 0; 
dP(n,n,n) = 0;
Km = klinkenberg(Pm);
Tgsc= trans(Pm);
Sgm=1;
B(:,:,:)= (Km * Az*Tgsc)/dz;
S(:,:,:)= (Km * Ay*Tgsc)/dy;
W(:,:,:)= (Km * Ax*Tgsc)/dx; 
E(:,:,:)= (Km * Ax*Tgsc)/dx; 
N(:,:,:)= (Km * Ay*Tgsc)/dy; 
A(:,:,:)= (Km * Az*Tgsc)/dz; 
X(:,:,:)= ((1)*(dx*dy*dz)/dt)*((Sgm*mat_por(Pm)*cmprs(Pm) *rho_sc()/(5.61458*Bg_factor(Pm)))+( mat_por(Pm)*cmprs(Pm)*(ad_vol(Pm)+de_vol(Pm))));
Q = -1*X*Pm;
C = (E+W+N+S+A+B-X);
tun(125,125)=0; 
lun(125,1)=0;

for y=1:int16(fix((T/dt)))
for x=1:125
[i,j,k]=index(x);
lun(x,1)=Q(i,j,k);

    
temp=(25*(i-1))+(5*(j-1))+k; 
tun(x,temp)= C(i,j,k);

i1 = i-1;
if i1>=1
    temp=(25*(i1-1))+(5*(j-1))+k;
    tun(x,temp)=W(i,j,k);
end
j1 = j-1; 
if j1>=1 
    temp=(25*(i-1))+(5*(j1-1))+k;
    tun(x,temp)=S(i,j,k);
end
k1 = k-1; 
if k1>=1 
    temp=(25*(i-1))+(5*(j-1))+k1; 
    tun(x,temp)=B(i,j,k);
end
i1=i+1;
if i1<=5
    temp=(25*(i1-1))+(5*(j-1))+k;
    tun(x,temp)=E(i,j,k);
end
j1=j+1; 
if j1<=5 
    temp=(25*(i-1))+(5*(j1-1))+k; 
    tun(x,temp)=N(i,j,k); 
end
k1=k+1;
if k1<=5
    temp=(25*(i-1))+(5*(j-1))+k1;
    tun(x,temp)=A(i,j,k);
end 
end 
sol=tun\lun;

for x=1:125
    [i,j,k]=index(x);
    dP(i,j,k)=sol(x);
end 

for i=1:n
    for j=1:n 
        for k=1:n 
            if y==1 
                P(i,j,k,y)= Pm -dP(i,j,k);
            else
                P(i,j,k,y)= P(i,j,k,y-1)-dP(i,j,k);
            end
        end
    end
end
for i=1:n
for j=1:n
for k=1:n
    
Km=klinkenberg( P(i,j,k,y) );
Tgsc = trans( P(i,j,k,y) );
B(i,j,k)= (Km * Az*Tgsc)/dz;
S(i,j,k)= (Km * Ay*Tgsc)/dy;
W(i,j,k)= (Km * Ax*Tgsc)/dx;
E(i,j,k)= (Km * Ax*Tgsc)/dx;
N(i,j,k)= (Km * Ay*Tgsc)/dy; 
A(i,j,k)= (Km * Az*Tgsc)/dz;
X(i,j,k)= ((1)*(dx*dy*dz)/dt)*((Sgm*mat_por(P(i,j,k,y))*cmprs(P(i,j,k,y))*rho_sc()/(5.61458 *Bg_factor(P(i,j,k,y))))+(mat_por(P(i,j,k,y))*cmprs(P(i,j,k,y))*(ad_vol(P(i,j,k,y))+ de_vol(P(i,j,k,y)))));
Q(i,j,k) = -1*X(i,j,k)*P(i,j,k,y); C(i,j,k) = (E(i,j,k)+W(i,j,k)+N(i,j,k)+S(i,j,k)+A(i,j,k)+B(i,j,k)-X(i,j,k));
end
end
   end
end
P1(n,n,n,m)=0;
for y=1:m
    for i=1:n 
        for j=1:n 
            for k=1:n
                P1(i,j,k,y)=P(k,i,j,y); 
            end
        end
    end
end

[Walter Roberson]

function klinkenberg
[...]
Km = klinkenberg(Pm);

Your function named klinkenberg appears to be attempting to call upon a different function named klinkenberg, which is a problem.

I do not appear to find an original source for your code, so I am unable to offer a solution.